Are advertisements becoming too cruel? That is the question being put to television watchdogs, as they investigate complaints that a series of recent ads have gone beyond offensive to just plain nasty.

Are advertisements becoming too cruel? That is the question being put to television watchdogs, as they investigate complaints that a series of recent ads have gone beyond offensive to just plain nasty.

The Independent Television Commission (ITC) is investigating complaints about advertising campaigns for, among others, Heinz, Red Devil, Tango and Vodka Source, amid claims that advertisers are attempting to tap into an increasingly aggressive and cynical youth culture.

One, for energy drink Red Devil, was recently moved to a time slot after the watershed of 9pm after it drew 183 complaints from viewers. In the commercial, hard-man footballer-turned-actor Vinnie Jones deliberately places a bird table behind a window so that a hungry robin flies into the glass, stunning itself.

Another campaign, for the drink brand Vodka Source, features two gaily sadistic Scandinavian blonde women, who in one advertisement take pleasure in burning an old man's coat, and in another, make an elderly man stand in freezing water and use his genitalia for fishbait.

Meanwhile, an ad for the once resolutely homely Heinz Salad Cream has attracted 111 complaints from viewers and homeless groups after it showed a vagrant buying a bottle of salad cream to enliven food he scavenged from dustbins - accompanied by the slogan: "Anything tastes supreme with Heinz Salad Cream".

And earlier this year, a commercial for soft drink Tango was withdrawn from screens after the ITC upheld the view of 83 complainants that it could encourage bullying. The advert showed an overweight boy being bullied by a gang of men shouting at him through megaphones for not drinking Tango. The boy was reduced to tears. The advert ended with viewers being encouraged to send off for a megaphone so they could "join in the fun".

The ads are not just restricted to the terrestrial channels. Music channel MTV recently ran an ad featuring a hillbilly family called the Jukka Brothers, one of whom is punished for "unsexy dancing" by having the MTV logo beaten into his bare behind with a bat.

John Beyer, director of the National Viewers' and Listeners' Association, has called for a shake-up of the regulatory system governing television advertisements to stem what he sees as an increase in "cruel" ads.

"Advertisements are becoming nastier and it is a very sad trend. Viewers are getting rather immune to the impact of television commercials, and for that reason advertisers are trying to make their adverts stand out," he says.

"It is time that the code of practice relating to advertising was overhauled and that the regulatory bodies took a far more strident approach to advertising standards, because the tastes of society are determined to a large extent by what we see on television."

But the ITC disputes the idea that television ads are getting nastier. A spokeswoman says: "I don't think it's getting more cruel - the Tango ads date back to the early 90s, such as the famous one with the slapping around the face - they were considered pretty cruel. And then there were the Martini ads, where it was described as "only for beautiful people". Personally I think those were in some way more groundbreaking and shocking than perhaps some of those more recent ones are. The Tango ads we upheld complaints about; they were very shocking at the time."

She said the problem with deciding whether an advertisement was "too cruel" was that it would fall under the commission's "offensiveness" guidelines, which were necessarily subjective.

"It's quite difficult because what's offensive to one person doesn't necessarily affect another - it isn't simply a black and white area. You get such a varying degree of complaints.

"An advertisement you could look at every evening and never consider to be offensive, we'll still get one or two complaints because people interpret it in a certain way. But it is also the area in which we uphold least complaints because you have to look at what the majority of people would find offensive."

Last year the ITC received 3,092 complaints about offensive advertisements, and upheld 9 of them. Whereas under its "misleading" guidelines, it received 2,074 complaints, and upheld 72.

Complaints are handled by individual officers in the first instance, and then, if deemed serious enough (such as in the case of the Tango "megaphone" ad, which was removed from screens) the decision is made at board level.

"We recognise that advertising is a creative medium, and there has to be scope for irony and humour, providing it's within legal, decent, honest and truthful framework," said the ITC spokeswoman.

"In the case of the Tango megaphone ads, which drew 60 or 70 complaints, the complaints were not upheld because they were cruel or offensive, but because they were harmful - we didn't want copycat incidences and the campaign is aimed directly at children.

"The whole reason we suspended it was because it was seen as a very deliberate bullying strategy, and what tipped it was when we started getting them from teachers and parents saying it would translate to the schoolyard."

Much of the decision depends on context - the lack of complaints about the Jukka brothers bottom-branding advertisement probably reflects the age and humour of MTV's viewing audience.

While the ITC has seen an upsurge in complaints about cruelty to men, beginning with the Diet Coke "bare chested builder" campaign, and now encompassing the Spirito di Punto campaign, where men and women make derogatory remarks about each others' handling of the car, the one area guaranteed to draw complaints is animal welfare.

Thus the Vinnie Jones advertisement has had to be moved back to the watershed, (the Advertising Standards Authority also received 3 complaints about the poster version - showing a stunned robin) while in 1998 an advert for Levi jeans, which featured a hamster called Kevin, first running on his wheel, then apparently as dead as a doornail, drew the most complaints from the public since public complaining began. (They were not upheld, but the advertisement was moved to a later slot).

Perhaps the most bizarre recent complaint concerns Graham the cartoon cow in Boddingtons advertisements. At least one viewer complained that he was promoting bestiality. As yet, the complaint has not been upheld.